I took the 850 to the Volvo dealer and they were great. They signed me up for "Volvo Service for Life" and took a look at it. Their conclusion was the Catalytic Converter is not working (remember I welded a rod into it to stop the rattle) and this was not from a hand held but the official OBDII reader for Volvo. They then offered an estimate of $1300 for the Cat alone plus labor. I have been at this long enough to report when an exhaust component goes bad... replace the whole thing. Too often I weld in or replace something only to go back in a few weeks or months to fix the another piece. So, I thanked them (they put in a thermostat too $155) and ordered a complete new system for about $650 and I'll put it in.
I am still hoping this will reset.... once I install the cat